Synthesis of ZnO Nanoparticles Doped with Cobalt: Influence of Doping on the Magnetic and Fluorescent Properties

Abstract

We have investigated the influence of cobalt doping on the luminescent and magnetic properties of ZnO nanoparticles prepared by co-precipitation. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and by use of a vibrating sample magnetometer (VSM). XRD analyses revealed a standard ZnO wurtzite crystal structure and showed that the cobalt doped ZnO nanoparticles (ZnO:Co_NPs) were synthetized without impurities. The calculation based on the XRD shows the average crystallite sizes of ZnO to be in the 8-11 nm range. TEM images of ZnO and ZnO:Co indicated that these nanoparticles are nearly uniformly spherical with a diameter of about 10 - 15 nm. The PL spectra exhibited high [low] intensity in the UV [visible] region. While the PL shows a decreasing intensity with increasing doping doses, the peak at 544nm is not present in the cobalt-doped zinc oxide, and a the peak at 378 nm shifts to 390nm. The VSM measurement confirmed the presence of ferromagnetism and we observed an increase in the values of the saturation magnetization with increasing Co concentration.